Scotsbard, in numerology, if you take those numbers and add each one to the next, always reducing to a single digit, like this:

1+0=1+8=9+3=12(or 1+2)= 3 which is also what you get if you just add the 21 (2+1) which you had. It's kind of neat the way the whole thing is inverted 21/12, yet can be reduced down to the same number. I really enjoy the logic and inevitability of numerology, just for playing around with numbers.

Thanks!

kat